Split in Three

input/code.cpp: In function 'void solve()':
input/code.cpp:59:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 100;

int t;
int n;

int Group[MAX_N];
int Sum[3] = { 0 };
bool found = false;

bool check()
{
    if(Sum[1] - Sum[0] == 1 && Sum[2] - Sum[1] == 1)
        return true;
    else
        return false;
}

void recur(int pos)
{
    if(pos == n)
    {
        if(check())
        {
            found = true;
            for(int i = 0; i < n; i++)
            {
                cout << Group[i] << " ";
            }
            cout << endl;
        }
        return;
    }

    if(Sum[0] > n*(n+1)/3 || Sum[1] > n*(n+1)/3 || Sum[2] > n*(n+1)/3)
    {
        return;
    }

    int WhichGroup[3] = {1, 2, 3};
    random_shuffle(WhichGroup, WhichGroup + 3);

    for(int i = 0; i < 3; i++)
    {
        Group[pos] = WhichGroup[i];
        Sum[WhichGroup[i]-1] += pos+1;
        recur(pos + 1);
        Sum[WhichGroup[i]-1] -= pos+1;
        if(found)
            return;
    }
}

void solve()
{
    scanf("%d", &n);
    if((n + 2) % 3 == 0)
    {
        puts("IMPOSSIBLE");
    }
    else
    {
        recur(0);
    }
}

int main()
{
    t = 1;
    //scanf("%d", &t);
    while(t--)
    {
        solve();
    }
    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: ACCEPTED

Test 8

Group: 1, 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 15

Group: 2

Verdict: ACCEPTED